My dynamo hub is one of these & I've had no problems with it. Ridden about three & a half thousand miles on it myself, not sure what mileage before I had it but I imagine at least the same again (bought the bike second-hand with dynamo hub & it had toured Europe on the current T785).
Are the 1.5V Shimano hubs (ie the £45 T785 that Spa Cycles are selling) any good? Front and rear lights only, no USB charging.